Three wire grounded receptacle with safety lock

ABSTRACT

A grounded receptacle to receive a conventional plug with two live sockets to receive the two live prongs of the plug and a grounded socket to receive the ground prong of the plug. Previous grounded receptacles of this type had the disadvantage that they were as equally suited to be used with plugs without a ground prong as with plugs with a ground prong. The grounded socket of this receptacle has at least one blocking plate which normally extends to a position blocking insertion of one of the live prongs of the plug into the corresponding live sockets of the receptacle, but which is resiliently displaced by insertion of a ground prong into the grounded socket to a position in which such insertion of the live prong is permitted.

UIlItGd States Patent 1 [1 1 3,736,547 Koenig [45] May 29, 1973 THREEWIRE GROUNDED Primary ExaminerMarvin A. Champion RECEPTACLE WITH SAFETYLOCK [76] Inventor: Gerhard Koenig, 58 Westview Crescent, Elliot Lake,Ontario, Canada [22] Filed: Sept. 22, 1971 [21] Appl. No.: 182,592

[52] US. Cl. ..339/14 R, 339/40 [51] Int. Cl. ..II01r 3/06 [58] Field ofSearch ..339/14, 74, 36, 37, 339/40, 41, 42, 43

[56] References Cited UNITED STATES PATENTS 3,173,731 3/1965 Anderson..339/14 R 2,579,538 12/1951 Bierce 339/14 R 3,238,492 3/1966 Houston..339/40 3,206,705 9/l965 Smith ...339/l4 R 3,363,215 l/1968 Smith..339/14 R FOREIGN PATENTS OR APPLICATIONS 377,352 7/l932 Great Britain..339/43 Assistant ExaminerRobert A. Hafer AttorneyGeorge H. Riches [57] ABSTRACT A grounded receptacle to receive a conventional plug withtwo live sockets to receive the two live prongs of the plug and agrounded socket to receive the ground prong of the plug. Previousgrounded receptacles of this type had I the disadvantage that they wereas equally suited to be used with plugs without a ground prong as withplugs with a ground prong. The grounded socket of this receptacle has atleast one blocking plate which normally extends to a position blockinginsertion of one of the live prongs of the plug into the correspondinglive sockets of the receptacle,

but which is resiliently displaced by insertion of a ground prong intothe grounded socket to a position in which such insertion of the liveprong is permitted.

10 Claims, 4 Drawing Figures PATENTEDMAYZB 1975 INVENTOR. GER HARDKOENIG THREE WIRE GROUNDED RECEPTACLE WITH SAFETY LOCK BACKGROUND OF THEINVENTION This invention relates generally to a grounded receptacle forreceiving a conventional three prong grounded electrical plug and moreparticularly to such a grounded receptacle having a Safety lock.

In the past electrical plugs having only two prongs and receptacleshaving two sockets to receive these prongs have been widely used toconnect various appliances or devices to a sourceof power. Thisarrangement has the disadvantage that it is not generally convenient toindependently connect the appliance or device to an electrical ground,while it is generally known that a lesser number of electrical firesoccur in appliances and wiring when provision is made for electricallygrounding the appliance or wiring.

More recently this disadvantage has been overcome to some extent by theuse of electrical plugs having a third prong called a ground prong withreceptacles having a third socket called a grounded socket. As is wellknown, the ground prong is connected through a third wire to theappliance or device with which it is used, while the grounded socket isconnected to an electrical ground. The term live prong is used to referto either of the prongs of such a plug other than the ground prong,while the term live socket is used to refer to either of the sockets ofsuch a receptacle other than the grounded socket. The ground prong ofthese conventional three prong plugs is generally shaped so that itcannot be inadvertently inserted into one of the live sockets of theseconventional grounded receptacles. This method of providing anelectrical ground has proven to be such a significant advantage that incertain installations in some areas only such grounded receptacles arepermitted to be installed. However these conventional groundedreceptacles still have the disadvantage that plugs which are notprovided with a ground prong or plugs with the ground prong broken offmay still be used in conjunction with them in which case the applianceor device which is plugged in is still not grounded.

In addition conventional grounded receptacles have the furtherdisadvantage that persons who are not aware of the danger involved, suchas small children, may receive a severe electrical shock resulting ininjury or death by inserting conductive objects into such a receptaclewhen it is not in use to make contact with the live sockets. One of theattempts to overcome this further disadvantage has been to provide a capfor each receptacle, but these caps have the disadvantage that if theyare removable they are often eventually lost and if they are notremovable they must be hinged or have some other way of being opened inwhich case they are often broken off. Also, such caps do not provideprotection to children who are old enough to be able to remove or openthem.

SUMMARY OF THE INVENTION Accordingly, it is an object of the presentinvention to at least partially overcome these disadvantages to providea safer grounded receptacle having a lock which restricts the liveprongs of a plug or any other conductive object from making contact withthe live sockets of the receptacle unless the ground plug or otherobject is inserted into the grounded socket of the receptacle.

To this end, in one of its aspects, the invention provides a groundedreceptacle to receive a conventional electrical plug which has first andsecond live prongs and a ground prong, comprising first and second liveprong socket means adapted to contact said first and second live prongs,and grounded socket means having ground prong receiving means and atleast one live prong blocking means, said ground prong receiving meansadapted to resiliently receive said ground prong,

said blocking means having a first position blocking contact of saidfirst live prong with said first live prong socket means, and a secondposition unblocking said contact, said blocking means being moved fromthe first position to the second position by partial entry of the groundprong into the ground prong receiving means and returned from the secondposition to the first position upon removal of the ground prong.

In another of its aspects, the invention further provides a groundedreceptacle to receive a conventional electrical plug which has first andsecond live prongs and a ground prong, comprising (a) a non-conductivebody having a non-conductive cover, said cover having first and secondopenings adapted to respectively receive said first and second liveprongs, and a further opening adapted to receive said ground prong, (b)first and second live prong sockets each having a rear portion and twoarms extending from said rear portion in opposed relation to form amouth, said first and second live prong sockets securedly located bysaid body to respectively engageably receive said first and second liveprongs inserted through said openings in said cover and through saidmouths, and (c) a grounded socket having a rear portion, two armsextending from said rear portion in opposed relation to form a mouth,said grounded socket securedly located by said body to resilientlyreceive through said mouth said ground prong inserted through saidfurther opening in said cover, and one blocking plate extending from oneof said arms to a normal position between said first opening in saidcover and the mouth of said first live prong socket blocking insertionof said first live prong into said first live prong socket, said one armbeing sufficiently resiliently displaced by insertion of the groundprong through the mouth of the grounded socket to displace said blockingplate to a displaced position in which insertion of said first liveprong into said first live prong socket is permitted.

Further objects and advantages of the invention will appear from thefollowing description, taken together with the accompanying drawings, inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cut-away perspective viewof the main component parts of a single grounded receptacle according toa preferred embodiment of the invention with a conventional three pronggrounded electrical plug shown in position to be inserted into thereceptacle,

FIG. 2 is a partially cut-away plan view of the embodiment of theinvention shown in FIG. 1,

FIG. 3 is a sectional view along lines III-III of FIG. 2, and

FIG. 4 is a similar view to FIG. 3, additionally showing a conventionalthree prong grounded electrical plug partially inserted in saidreceptacle.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference is first made to FIGS.1 to 3 which show a single grounded receptacle according to theinvention having the main component parts of two live sockets 12 and 12and a grounded socket 14. As best seen in FIG. 1, these sockets areformed having appropriate dimensions and suitably located with respectwith each other so as to be able to receive a conventional three pronggrounded electrical plug 16 having two live prongs l8 and 18' and oneground prong 20. In practice, receptacles according to the invention areseen as being used primarily with conventional voltages of 115 or 220volts and currents up to 50 amperes although they could be constructedto withstand substantially higher voltages and currents. It may bedesirable to combine the components described herein in multiples toform double or triple receptacles rather than the singlereceptacledescribed herein.

The sockets are held in place by a body 22 formed of a suitablenon-conducting material, havinga cover 24. As seen in FIG. 2, the cover24 has two slots 26, 26 and a circular opening 28 to permit insertion ofthe prongs of the plug 16 into the corresponding sockets of thereceptacle 10.

The live sockets l2 and 12' are each formed of relatively thinconductive material to have a rear portion 30, 30' and a first arm 31,31' and a second arm 32, 32' extending from the rear portion 30, 30 toform a mouth 33, 33'. As shown, extending from the rear portions 30,30', the arms of each of the live sockets consist of a pair of firstportions 34, 34' extending substantially parallel to each other, a pairof second portions 35, 35' converging towards each other and a pair ofthird portions 36, 36 diverging from each other to form the mouth 33,33'. Each live socket 12, 12' also has a terminal 37, 37' to which anappropriate wire is connected to supply an electrical power supply tothe receptacle. The live sockets 12 and 12' may be formed of anysuitable material and in any suitable shape to provide electricalcontact between them and the respective live prongs 18 and 18 when theplug 16 is fully inserted into the receptacle 10. These may take theform of a variety of electrical contacts known to those familiar withthe art.

The grounded socket 14 which is shown as being somewhat larger than thelive sockets 12, 12, is similarly formed of relatively thin material tohave a rear portion 38 and a first arm 39 and a second arm 40 whichextends from the rear portion 38 to form a mouth 41. The arms 39,40 ofthe grounded socket 14 are similarly formed to have a pair of firstportions 42 extending substantially parallel to each other, a pair ofsecond portions 43 converging towards each other and a pair of thirdportions 44 diverging from each other to form the mouth 41. The groundedsocket 14 also has a connection 45 to which a grounding lead isconnected.

The grounded socket 14 additionally is shown having blocking plates 46and 47 extending respectively from arms 39 and 40. When the plug 16 isin position for insertion into the receptacle l0, blocking plate 46 islocated in a position between live prong 18 and the mouth 33 of thecorresponding live socket 12, and blocking plate 47 is located in aposition between live prong l8 and the mouth 33' of the correspondinglive socket 12. Although a blocking plate 46, 47 is shown extending fromeach 39, 40 of the grounded socket 14, the grounded socket 14 may beconstructed to have the two blocking plates extending from a single armor alternately even with a single blocking plate extending from a singlearm (although this is not as advantageous as it leaves one of the livesockets 12, 12 open to insertion of a conductive object).

There are a variety of materials of which the grounded socket 14 may beformed in a variety of shapes to provide electrical contact with theground prong 20 when the plug 16 is fully inserted into the receptacle10 in addition to being sufficiently resilient to provide that theblocking plates, which are resiliently displaced by insertion of theground prong 20 as described below, return to their originalposition'when the ground plug is withdrawn.

As an alternate to the embodiment of the invention shown in thedrawings, the grounded socket 14 may be located in the body 22 somewhathigher than shown with respect to the live sockets 12, 12' andconstructed to have the blocking plates 46, 47 attached to therespective arms 39, 40 of the grounded socket 14 so as to locate theblocking plates 46, 47 at a level somewhat below the mouth 41 of thegrounded socket 14. This enables the receptacle to be used with a threeprong plug having a ground prong 20 of a different length with respectto the live prongs 20 than that shown. In fact, such a receptacle mayeven be used with a plug having a ground prong 20 shorter in length thanthe live prongs 18, 18 in which case the grounded socket 14 may besmaller than the live sockets 12, 12.

The blocking plates 46, 47 are shown as being formed of the same pieceof thin conductive material as the arms 39, 40 and the rear portion 38of the grounded socket 14, and as being located in a plane perpendicularto the direction of insertion (shown by arrow M in FIG. 1) of the plug16 into the receptacle 10. While the blocking plates 46, 47 need notnecessarily be of this shape nor located in this plane, they must beshaped and normally located so as to contacted by an object which isinserted through one of the slots 26, 26' in the cover 24 and notreadily moved aside by pressure on such object to permit such object tocontact one of the live sockets 12, 12'. Therefore, as is apparent fromthe foregoing, the location or position of the blocking plates 46, 47 isto some extent dependent upon their shape.

It is preferable that the blocking plates 46, 47 not be conductive sothat when the plug 16 is in place in the receptacle 10, the possibilityis reduced of one of the live prongs 18, 18 shorting to ground throughone of the blocking plates 46, 47. This may be achieved by covering theblocking plates 46, 47 with a suitable insulating covering 48 as shownor alternately by forming the blocking plates 46, 47 of a suitableinsulating material and attaching them to the arms 39, 40 of thegrounded socket 14.

In use, a receptacle according to the invention performs a form oflocking function in that it is necessary to insert an object, such as aground prong of a conventional three prong plug, into the groundedsocket 14 in order to gain access to the live sockets l2, 12. As bestseen in FIG. 3, each of the blocking plates 46, 47 is normally locatedbetween one of the slots 26, 26' in the cover 24 and the correspondingone of the mouths 33, 33 of the live sockets 12, 12' in which positioninsertion of one of the live prongs 18, 18' or other conductive objectthrough that slot to make contact with the live socket is blocked.However, as seen in FIG. 4, when the ground prong 20 is inserted throughthe circular opening 28 in the cover 24 into the mouth 41 of thegrounded socket 14, the arms 39, 40 of the grounded socket 14 are pushedapart by the ground prong 20. This motion of the arms moves the blockingplates 46, 47 which are attached to the arms, to the positions shown inFIG. 4, wherein entry of the live prongs 18, 18 into the mouths 33, 33'of the respective live sockets l2, 12 is not blocked. The groundedsocket 14 has sufficient resilience that when the ground prong 20 isremoved from the mouth 41 of the grounded socket 14, the arms 39, 40 andthe blocking plates 46, 47 of the grounded socket 14 return to theiroriginal or normal positions blocking access to the live sockets 12,12'.

What I claim is:

1. A grounded receptacle to receive a conventional electrical plug whichhas first and second live prongs and a ground prong, comprising:

first and second live prong socket means adapted to contact said firstand second live prongs, and grounded socket means having ground prongreceiving means and at least one live prong blocking means comprised ofan integral extension of the ground prong receiving means, said groundprong receiving means adapted to resiliently receive said ground prong,said blocking means having a first position blocking contact of saidfirst live prong with said first live prong socket means, and a secondposition unblocking said contact, said blocking means being moved fromthe first position to the second position by partial entry of the groundprong into the ground prong receiving means and returned from the secondposition to the first position upon removal of the ground prong.

2. A grounded receptacle as claimed in claim 1, wherein said groundedsocket means has second integral live prong blocking means, said secondblocking means having a first position blocking contact of said secondlive prong with said second live prong socket means, and a secondposition unblocking said contact, said second blocking means being movedfrom the first position to the second position by partial entry of saidground prong into the ground prong receiving means and returned from thesecond position to the first position upon removal of the ground prong.

3. A grounded receptacle as claimed in claim 1 wherein said live prongblocking means is located in a plane substantially perpendicular to thedirection of insertion of said plug into said receptacle.

4. A grounded receptacle as claimed in claim 2 wherein said live prongblocking means is coated with a suitable insulating material.

5. A grounded receptacle as claimed in claim 1 wherein said ground prongreceiving means and said live prong blocking means are formed of thinconductive material, said live prong blocking means being covered withsuitable insulating material. A

6. A grounded receptacle to receive a conventional electrical plug whichhas first and second live prongs and a ground prong, comprising:

a. a non-conductive body having a non-conductive cover, said coverhaving first and second openings adapted to respectively receive saidfirst and second live prongs, and a further opening adapted to receivesaid ground prong,

b. first and second live prong sockets each having a rear portion andtwo arms extending from said rear portion in opposed relation to form amouth, said first and second live prong sockets securedly located bysaid body to respectively engageably receive said first and second liveprongs inserted through said openings in said cover and through saidmouths, and

c. a grounded socket having a rear portion, two arms extending from saidrear portion in opposed relation to form a mouth, said grounded socketsecuredly located by said body to resiliently receive throughsaid mouthsaid ground prong inserted through said further opening in said cover,and one blocking plate integral with and extending from one of said armsto a normal position between said first opening in said cover and themouth of said first live prong socket blocking insertion of said firstlive prong into said first live prong socket, said one arm beingsufficiently resiliently displaced by insertion of the ground prongthrough the mouth of the grounded socket to displace said blocking plateto a displaced position in said insertion of said first live prong intosaid first live prong socket is permitted.

7. A grounded receptacle as claimed in claim 6 wherein said groundedsocket has a second blocking plate integral with and extending from asecond of said arms to a normal position between said second opening insaid cover and the mouth of said second live prong socket blockinginsertion of said second live prong into said second live prong socket,said second arm being sufficiently resiliently displaced by insertion ofthe ground prong through the mouth of the grounded socket to displacesaid second blocking plate to a displaced position in which insertion ofsaid second live prong into said second live prong socket is permitted.

8. A grounded receptacle as claimed in claim 7 wherein said blockingplates are located in a plane substantially perpendicular to thedirection of insertion of said plug into said receptacle.

9. A grounded receptacle as clamed in claim 7 wherein said blockingplates are coated with a suitable insulating material.

10. A grounded receptacle as claimed in claim 7 wherein said groundedsocket is formed of a thin conductive material, said blocking platesbeing covered with a suitable insulating material. l 4

1. A grounded receptacle to receive a conventional electrical plug whichhas first and second live prongs and a ground prong, comprising: firstand second live prong socket means adapted to contact saId first andsecond live prongs, and grounded socket means having ground prongreceiving means and at least one live prong blocking means comprised ofan integral extension of the ground prong receiving means, said groundprong receiving means adapted to resiliently receive said ground prong,said blocking means having a first position blocking contact of saidfirst live prong with said first live prong socket means, and a secondposition unblocking said contact, said blocking means being moved fromthe first position to the second position by partial entry of the groundprong into the ground prong receiving means and returned from the secondposition to the first position upon removal of the ground prong.
 2. Agrounded receptacle as claimed in claim 1, wherein said grounded socketmeans has second integral live prong blocking means, said secondblocking means having a first position blocking contact of said secondlive prong with said second live prong socket means, and a secondposition unblocking said contact, said second blocking means being movedfrom the first position to the second position by partial entry of saidground prong into the ground prong receiving means and returned from thesecond position to the first position upon removal of the ground prong.3. A grounded receptacle as claimed in claim 1 wherein said live prongblocking means is located in a plane substantially perpendicular to thedirection of insertion of said plug into said receptacle.
 4. A groundedreceptacle as claimed in claim 2 wherein said live prong blocking meansis coated with a suitable insulating material.
 5. A grounded receptacleas claimed in claim 1 wherein said ground prong receiving means and saidlive prong blocking means are formed of thin conductive material, saidlive prong blocking means being covered with suitable insulatingmaterial.
 6. A grounded receptacle to receive a conventional electricalplug which has first and second live prongs and a ground prong,comprising: a. a non-conductive body having a non-conductive cover, saidcover having first and second openings adapted to respectively receivesaid first and second live prongs, and a further opening adapted toreceive said ground prong, b. first and second live prong sockets eachhaving a rear portion and two arms extending from said rear portion inopposed relation to form a mouth, said first and second live prongsockets securedly located by said body to respectively engageablyreceive said first and second live prongs inserted through said openingsin said cover and through said mouths, and c. a grounded socket having arear portion, two arms extending from said rear portion in opposedrelation to form a mouth, said grounded socket securedly located by saidbody to resiliently receive through said mouth said ground pronginserted through said further opening in said cover, and one blockingplate integral with and extending from one of said arms to a normalposition between said first opening in said cover and the mouth of saidfirst live prong socket blocking insertion of said first live prong intosaid first live prong socket, said one arm being sufficientlyresiliently displaced by insertion of the ground prong through the mouthof the grounded socket to displace said blocking plate to a displacedposition in which insertion of said first live prong into said firstlive prong socket is permitted.
 7. A grounded receptacle as claimed inclaim 6 wherein said grounded socket has a second blocking plateintegral with and extending from a second of said arms to a normalposition between said second opening in said cover and the mouth of saidsecond live prong socket blocking insertion of said second live pronginto said second live prong socket, said second arm being sufficientlyresiliently displaced by insertion of the ground prong through the mouthof the grounded socket to displace said second blocking plate to adisplaced position in which insertion of said second live prong intosaid second lIve prong socket is permitted.
 8. A grounded receptacle asclaimed in claim 8 wherein said blocking plates are located in a planesubstantially perpendicular to the direction of insertion of said pluginto said receptacle.
 9. A grounded receptacle as clamed in claim 7wherein said blocking plates are coated with a suitable insulatingmaterial.
 10. A grounded receptacle as claimed in claim 7 wherein saidgrounded socket is formed of a thin conductive material, said blockingplates being covered with a suitable insulating material.